Uplink path integrity detection in distributed antenna systems

ABSTRACT

Aspects and features are directed to an uplink integrity detection sub-system. In one aspect, a distributed antenna system is provided that includes at least one master unit; a plurality of remote antenna units each in communication with the at least one master unit; and a system controller configured to: determine a noise figure for an uplink path from at least one of the plurality of remote antenna units; and modify a gain of the uplink path when the noise figure exceeds a desired threshold, wherein the noise figure is determined as a function of a measured signal power of an undesirable signal component in the uplink path from the remote antenna unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of U.S. patentapplication Ser. No. 14/428,254, titled “UPLINK PATH INTEGRITY DETECTIONIN DISTRIBUTED ANTENNA SYSTEM” filed on Mar. 13, 2015, which is a U.S.national phase under 35 U.S.C. 371 of International Patent ApplicationNo. PCT/EP2012/003849, titled “Uplink Path Integrity Detection inDistributed Antenna Systems” and filed Sep. 14, 2012, the entirety ofeach of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates generally to telecommunications systems and moreparticularly relates to reducing impacts of undesirable signalcomponents from remote antenna units in distributed antenna systems.

BACKGROUND

A distributed antenna system can include multiple remote antenna unitsin communication with a master unit. In the uplink direction, uplinksignals from the remote antenna units are combined at the master unit.Each of the uplink signals can include undesirable signal components,such as noise or interfering signals, added to the uplink signals by theremote antenna unit or other source. Uplink paths from different remoteantenna units to the master unit can be characterized by differentsignal gains. Consequently, the remote antenna units can contributedifferent amounts of noise to the combined uplink signal generated bythe master unit.

Uplink signals including undesirable signal components can be combinedwith other uplink signals by, for example, a master unit of adistributed antenna system. Combining uplink signals includingundesirable signal components with other uplink signals can causecorruption of data or other information communicated via the uplinksignals, thereby decreasing the signal coverage provided by thedistributed antenna system.

Systems and methods that can identify undesirable signal components ofone or more remote antenna units to determine the integrity of an uplinkpath are desirable.

SUMMARY

Certain aspects and features of the present invention are directed to anuplink integrity detection sub-system. In one aspect, a distributedantenna system is provided. The distributed antenna system includes aremote antenna unit that can communicate with wireless devices in acoverage area, one or more additional remote antenna units that cancommunicate with wireless devices in one or more additional coverageareas, and a unit that can communicate with the remote antenna unit andthe one or more additional remote antenna units. The unit includes adistributed antenna system controller. The distributed antenna systemcontroller can determine that an undesirable signal component having asignal power exceeding a threshold power is communicated via an uplinkpath from the remote antenna unit. The distributed antenna systemcontroller can also minimize an impact of the undesirable signalcomponent on the additional coverage areas of the one or more additionalremote antenna units. Minimizing the impact can include modifying thegain of the uplink path over which the undesirable signal component iscommunicated and thereby added to combined signals communicated from theone or more additional remote antenna units.

In another aspect, an uplink integrity detection sub-system is provided.The uplink integrity detection sub-system includes a test signalgenerator disposed in a remote antenna unit of a distributed antennasystem, a power detector disposed in a unit of the distributed antennasystem, and a distributed antenna system controller disposed in theunit. Non-limiting examples of a unit can include a master unit, anuplink measurement receiver, a base station router or other point ofinterface (“POI”), and the like. The unit can communicate with multipleremote antenna units of the distributed antenna system. The test signalgenerator can provide a test signal to an uplink path of the distributedantenna system. The power detector can measure, at a measurement pointan output power of the test signal. An example of a measurement pointcan include (but is not limited to) the input to a combiner of a masterunit. The output power of the test signal can be a function of an inputpower of the test signal as modified by the test signal traversing theuplink path from the remote antenna unit. The distributed antenna systemcontroller can determine a noise figure of the remote antenna unit basedon the output power of the test signal and the input power of the testsignal. In some aspects, the distributed antenna system controller cancontrol other components of the uplink integrity detection sub-system.

In another aspect, an uplink integrity detection sub-system is providedthat includes a remote antenna unit of a distributed antenna system. Theremote antenna unit includes a measurement receiver and a controller.The measurement receiver can measure the signal power of an undesirablesignal component having a frequency in an uplink frequency band used bythe remote antenna unit for communicating uplink signals. The controllercan determine that the signal power of an undesirable signal componentexceeds a threshold signal power. The controller can configure anattenuator disposed in the remote antenna unit to attenuate the uplinksignal based on the signal power of the undesirable signal component.

These illustrative aspects and examples are mentioned not to limit ordefine the invention, but to provide examples to aid understanding ofthe inventive concepts disclosed in this application. Other aspects,advantages, and features of the present invention will become apparentafter review of the entire application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a base station coupled to a DAS that has anuplink integrity detection sub-system according to one aspect.

FIG. 2 is a block diagram of a DAS in which an uplink integritydetection sub-system can be disposed according to one aspect.

FIG. 3 is a block diagram of an uplink integrity detection sub-systemincluding an uplink measurement receiver according to one aspect.

FIG. 4 is a block diagram of a remote antenna unit having a test signalgenerator of an uplink integrity detection sub-system according to oneaspect.

FIG. 5 is a flow chart illustrating a process for minimizing the noisecontribution of a remote antenna unit having an excessive noise figurein a DAS according to one aspect.

FIG. 6 depicts a flow chart illustrating a process for reducing thenoise contribution of remote antenna units in a DAS according to oneaspect.

FIG. 7 is a block diagram of components of an uplink integrity detectionsub-system included in a remote antenna unit for minimizing interferingsignals according to one aspect.

FIG. 8 is a block diagram of components of an uplink integrity detectionsub-system included in a master unit for minimizing interfering signalsaccording to one aspect.

DETAILED DESCRIPTION

Certain aspects and examples are directed to an uplink integritydetection sub-system that can be disposed in a distributed antennasystem (“DAS”). For example, a DAS can include a unit, such as a masterunit, in communication with multiple remote antenna units. Each remoteantenna unit can communicate with wireless devices in a respectivecoverage area. The master unit or another unit can include a systemcontroller. The system controller can determine that an undesirablesignal component having a signal power exceeding a threshold power isbeing communicated via an uplink path from a remote antenna unit. Anundesirable signal component can include any component that can corruptthe integrity of a first uplink signal or a second uplink signalcombined with the first uplink signal. Corrupting an uplink signal caninclude overdriving one or more devices of the DAS such that informationtransmitted via the uplink signal is lost or otherwise degraded. Thesystem controller can minimize an impact of the undesirable signalcomponent on coverage areas of other remote antenna units by modifyingthe gain of the uplink path over which the undesirable signal componentis communicated.

In some aspects, minimizing an undesirable signal component can includereducing a noise contribution from a remote antenna unit. An uplinkintegrity detection sub-system can minimize the noise contribution. Theuplink integrity detection sub-system can include a test signalgenerator disposed in one or more remote antenna units of a DAS, a powerdetector disposed in a master unit or other unit of the DAS, and a DAScontroller disposed in the unit. The test signal generator can provide atest signal to an uplink path of the DAS. The power detector canmeasure, at a measurement point, an output power of the test signal. Theoutput power of the test signal can be a function of an input power ofthe test signal as modified by the test signal traversing the uplinkpath.

The DAS controller can determine a noise figure of the remote antennaunit based on the output power of the test signal and the input power ofthe test signal. The DAS controller can determine that the noise figureis excessive for a given remote antenna unit among a group of remoteantenna units. The excessive noise contribution can prevent a basestation from distinguishing a signal from another remote antenna unitfrom the noise caused by the remote antenna unit having an excessivenoise figure. An excessive noise figure can exceed a desired threshold.The threshold can be, for example, the noise figure of the remoteantenna unit when the DAS is tested in a testing environment or otherproduction environment. Examples of an excessive noise contribution of aremote antenna unit can include, but are not limited to, a noise levelwith a power greater than the maximum specified by a manufacturer of aremote antenna unit or a noise level with a power greater than thatcaused by a noise figure determined for the remote antenna unit in atesting environment or other production environment. A testingenvironment can be, for example, a DAS including one or more masterunits and one or more remote antenna units. The testing environment orother production environment can measure different parameters, such asgain or noise figure, of the components of a DAS, such as the masterunits and remote antenna units. For example, in a testing environment orother production environment, it can be determined that a remote antennaunit in having a noise figure in excess of 7 dB can result in anexcessive noise contribution from the remote antenna unit. The thresholdnoise figure can therefore be determined as 7 dB. The remote antennaunit having the excessive noise figure can cause an excessive noisecontribution relative to the noise contribution from each of the otherremote antenna units in communication with the master unit. Theexcessive noise contribution can, for example, prevent the base stationfrom distinguishing signals from the other remote antenna units from thenoise of the remote antenna unit having the excessive noise figure.

The uplink integrity detection sub-system can compensate for the noisecontribution of a remote antenna unit having an excessive noise figureby determining a noise figure and output noise floor for an uplink pathfrom each remote antenna unit prior to combining uplink paths at amaster unit or any other node in the DAS. In some aspects, the uplinkintegrity detection sub-system can reduce the gain of an uplink pathfrom the remote antenna unit having the excessive noise figure. In otheraspects, the uplink integrity detection sub-system can increase the gainof uplink paths from remote antenna units not having an excessive noisefigure. In other aspects, the uplink integrity detection sub-system canadjust the gain of uplink paths from the remote antenna units incommunication with the master unit so as to equalize the noisecontributed by each remote antenna unit at the input to a combiner, sucha summer, in the master unit.

In additional or alternative aspects, minimizing an undesirable signalcomponent can include minimizing or otherwise controlling an undesirablesignal component that is an interfering signal received by a remoteantenna unit. An interfering signal can include an extraneous signalreceived by a remote antenna unit having a frequency within an uplinkfrequency band. An interfering signal can include an intermodulationproduct having a frequency within an uplink frequency band that isgenerated by extraneous signals received by the remote antenna unit.

The uplink integrity detection sub-system can include a measurementreceiver and a controller disposed in one or more remote antenna units.The measurement receiver can measure the signal power of an interferingsignal received by the remote antenna unit. The controller can determinethat the signal power of the interfering signal exceeds a thresholdsignal power. The controller can configure an attenuator disposed in theremote antenna unit to attenuate the uplink signal based on the signalpower of the interfering signal. The controller can also generate acontrol message for transmission to a master unit receiving the uplinksignal. The control message can specify additional adjustments to thegain of the uplink paths from to the master unit.

Detailed descriptions of certain aspects are discussed below. Theseillustrative examples are given to introduce the reader to the generalsubject matter discussed here and are not intended to limit the scope ofthe disclosed concepts. The following sections describe variousadditional aspects and examples with reference to the drawings in whichlike numerals indicate like elements, and directional descriptions areused to describe the illustrative examples but, like the illustrativeexamples, should not be used to limit the present invention.

FIG. 1 depicts an uplink integrity detection sub-system 13 disposed in aDAS 10. The DAS 10 in FIG. 1 also includes a downlink path 14 and anuplink path 16. The downlink path 14 can be used for communicatingdownlink signals from a base station 12 to a remote antenna unit.Downlink signals are signals at frequencies in a downlink frequency bandprovided from a base station 12 to a remote antenna for radiation towireless devices. The uplink path 16 can be used for communicatinguplink signals from a remote antenna unit to the base station 12. Uplinksignals are signals at frequencies in an uplink frequency band that arerecovered by a remote antenna from wireless devices in a coverage areaserviced by the remote antenna unit. In some aspects, the DAS 10 can bea system, such as (but not limited to) a time-division duplexing (“TDD”)system, using the same frequency band for communicating both downlinksignal and uplink signals.

Uplink signals transported over the links provided by different remoteantenna units or otherwise communicated via uplink paths from differentremote antenna units can be combined at a master unit. The uplinkintegrity detection sub-system 13 can compensate for the noisecontribution of remote antenna units having excessive noise figures tothe combined uplink signal traversing the uplink path 16.

FIG. 2 depicts an exemplary DAS 10 having base station routers 112 a,112 b in communication with base stations 12 a-n and a switch matrix114. The DAS 10 can also include master units 118 a-d in communicationwith zone combiners 116 a, 116 b and the remote antenna units 120 a-h.Each of the zone combiners 116 a, 116 b can combine uplink signals frommore than one master unit and provide a combined uplink signal to one ofthe base station routers 112 a, 112 b selected via the switch matrix114. In some aspects, the switch matrix 114 and zone combiners 116 a,116 b can be omitted and the master units 118 a-d can communicatedirectly with base station router 112 a or base station router 112 b.The DAS 10 can be positioned in an area to extend wireless communicationcoverage.

In the direction of a downlink path 14, the DAS 10 can receive signalsfrom the base stations 12 a-n via a wired or wireless communicationmedium. Downlink signals can be received by the base station routers 112a, 112 b. The base station routers 112 a, 112 b can provide the downlinksignals to the master units 118 a-d via the switch matrix 114 and thezone combiners 116 a, 116 b. The master units 118 a-d can communicatewith the zone combiners 116 a, 116 b via any communication mediumcapable of carrying signals between the zone combiners 116 a, 116 b andthe master units 118 a-d. Examples of a suitable communication mediuminclude copper wire (such as a coaxial cable), optical fiber, andmicrowave or optical link. The link can transport the signals in analogor in digitized form.

The master units 118 a-d can provide downlink signals to the remoteantenna units 120 a-h. The remote antenna units 120 a-h can communicatewith the master units 118 a-d via any communication medium capable ofcarrying signals between the master units 118 a-d and the remote antennaunits 120 a-h. Examples of a suitable communication medium includecopper wire (such as a coaxial cable), optical fiber, and microwave oroptical link. The link can transport the signals in analog or indigitized form. The remote antenna units 120 a-h can radiate the signalsof the sector(s) distributed to the physical area.

In the direction of an uplink path 16, the base station routers 112 a,112 b can receive uplink signals from remote antenna units 120 a-h viathe master units 118 a-d, the zone combiners 116 a, 116 b, and theswitch matrix 114. Uplink signals can include signals received fromwireless devices in the coverage zones serviced by the remote antennaunits 120 a-h.

An uplink integrity detection sub-system 13 can be disposed in the DAS10 depicted in FIG. 2. One or more components of the uplink integritydetection sub-system 13 can be disposed in one or more of the componentsof the DAS 10.

Noise Compensation

In some aspects, the uplink integrity detection sub-system 13 caninclude one or more devices for minimizing an undesirable signalcomponent that is an excessive noise contribution by a remote antennaunit. In some aspects, the uplink integrity detection sub-system 13 cancompensate for the noise contribution of remote antenna units havingexcessive noise figures in a DAS being commissioned. Commissioning a DAScan include installing, configuring, and calibrating the components ofthe DAS. In other aspects, the uplink integrity detection sub-system 13can compensate for the noise contribution of remote antenna units havingexcessive noise figures in a DAS that is operating.

FIG. 3 depicts an aspect of an uplink integrity detection sub-system 13including an uplink measurement receiver 203 and components disposed ina master unit 118.

The uplink measurement receiver can include a DAS controller 212, amodem 214, a power detector 218, a selective filter 219 and switches220, 222. The uplink measurement receiver 203 can determine the noisefigure for a test signal from each remote antenna unit. The noise figurecan be measured or otherwise determined at a measurement point in theuplink path prior to a combiner, such as a summer, in the master unit.The uplink measurement receiver 203 can selectively determine therespective noise contributions and noise figures of different remoteantenna units prior to a combiner in different master units.

The uplink integrity detection sub-system 13 can also include aprocessor 202, a modem 204, and a switch 208 disposed in the master unit118. The master unit 118 can also include a splitter module 206 in thedownlink path 14 and a combiner module 210 in the uplink path 16.Examples of the splitter module 206 can include a de-multiplexer,de-serializer, or an optical splitter. The master unit can also includeprogrammable gain amplifiers 209 a-d.

The DAS controller 212 can configure the components of the uplinkintegrity detection sub-system 13. An example of a DAS controller 212 isa Peripheral Interface Controller (“PIC”). The DAS controller 212 cancommunicate with components of the uplink integrity detection sub-system13 disposed elsewhere in the DAS 10 (e.g., in the master units, theremote antenna units, etc.) via the modem 214. The modem 214 cancommunicate control signals from the DAS controller 212 with the masterunit 118 via the downlink path 14 and uplink path 16. The master unit118 can communicate with the DAS controller 212 via modem 204. Themaster unit 118 can also transmit control signals to the remote antennaunits via the splitter module 206. The DAS controller 212 can alsoselectively communicate with different master units disposed indifferent downlink paths via switches 220, 222.

In additional or alternative aspects, the modem 214 can communicatecontrol signals to components of the uplink integrity detectionsub-system 13 disposed elsewhere in the DAS 10 via a control pathseparate from the downlink path 14 or uplink path 16. The control pathcan be any communication medium suitable for wired or wirelesscommunication between components of the uplink integrity detectionsub-system 13. Examples of a suitable communication medium includecopper wire (such as a coaxial cable), optical fiber, and microwave oroptical link.

The uplink measurement receiver 203 can measure the power of a testsignal traversing an uplink path from a remote antenna unit beinganalyzed to the master unit 118 at a measurement point at the input tothe combiner module 210. The combiner module 210 can combine uplinksignals from different remote antenna units into a combined uplinksignal. The combiner module 210 can be, for example, a summer. Themaster unit 118 can provide the combined uplink signal to a zonecombiner. The uplink measurement receiver 203 can receive the testsignal via the switch 222. The DAS controller 212 can communicate acontrol signal to the processor 202 of the master unit 118 to select aparticular remote antenna unit via switch 208.

The power detector 218 in uplink measurement receiver 203 can measurethe power of the test signal routed from a point in the uplink path 16prior to the combiner module 210. The power detector 218 can be, forexample, a logarithmic (“LOG”) power detector or a root means square(“RMS”) power detector. The DAS controller 212 in uplink measurementreceiver 203 can select different master units via switch 222 anddifferent uplink paths in each master unit via switch 208. The power ofthe test signal can be, for example, an amplification or othermodification of the input power of the test signal provided to an uplinkpath 16 from the remote antenna unit being analyzed. The modification ofthe input power can be caused by the test signal traversing the uplinkpath 16 from a remote antenna unit 120 to the master unit 118 at theinput of the combiner module 210. The power detector 218 can communicatedata representing the power of the test signal to the DAS controller212.

In some aspects, the power detector 218 can include a selective filter219 to remove extraneous signal components from the test signal prior tothe power detector 218 measuring the power of the test signal.Extraneous signal components can include, for example, signal componentsfrom uplink signals provided to the uplink path 16 by remote antennaunits other than the remote antenna unit being analyzed by the uplinkintegrity detection sub-system 13.

In additional or alternate aspects, the uplink measurement receiver 203can include a narrow-band filter. The narrow-band filter can reject orattenuate signal components interfering with the test signal. Examplesof signal components interfering with the test signal can include uplinksignals recovered during operation of the DAS.

Although FIG. 3 depicts the uplink measurement receiver 203 as aseparate device, the uplink measurement receiver 203 can be disposed inother components of the DAS. The uplink measurement receiver 203 can bedisposed in the DAS 10 at one or more measurement points. In someaspects, the uplink measurement receiver 203 can be disposed in one ormore base station routers 112 a, 112 b. In other aspects, the uplinkmeasurement receiver 203 can be disposed in one or more zone combiners116 a, 116 b. In other aspects, the uplink measurement receiver 203 canbe disposed in one or more master units 118 a-d.

A test signal can be provided to the uplink path at a remote antennaunit 120. For example, FIG. 4 depicts an aspect of a remote antenna unit120 having a test signal generator 302 of the uplink integrity detectionsub-system 13. Components of the uplink integrity detection sub-system13 in addition to the test signal generator 302 can include theprocessor 304, the modem 306, and the frequency scanner 320. The remoteantenna unit 120 can also include the power amplifier 308, the isolationsub-system 310, the low noise amplifier 312, and an antenna 314.

The remote antenna unit 120 can receive downlink signals via thedownlink path 14 and provide uplink signals via the uplink path 16. Theisolation sub-system 310 can isolate downlink signals traversing thedownlink path 14 and transmitted via the antenna 314 from uplink signalstraversing the uplink path 16 and recovered via the antenna 314. Theisolation sub-system 310 can be, for example, a duplexer.

The test signal generator 302 can be communicatively coupled to theantenna 314. The test signal generator 302 can provide a test signal tothe uplink path 16 via a coupler 316 at an uplink input to the isolationsub-system 310. The test signal generator 302 can be, for example, ananalog signal generator capable of producing continuous wave tones. Thetest signal generator 302 can be configured by the processor 304.

The processor 304 can configure the test signal generator 302 toincrease the power and/or change the frequency of the test signal inresponse to the control signals. The processor 304 can receive controlsignals from the DAS controller 212 communicated via the modem 306. Insome aspects, the modem 306 at the remote antenna unit 120 cancommunicate with modem 214 of the uplink measurement receiver 203. Inother aspects, the modem 306 at the remote antenna unit 120 cancommunicate with modem 204 of the master unit 118. The modem 306 cancommunicate with modems 204, 214 via the downlink path 14 and uplinkpath 16. In additional or alternative aspects, the modem 306 cancommunicate with modems 204, 214 via a control path. The control pathcan be any communication medium suitable for wired or wirelesscommunication between components of the uplink integrity detectionsub-system 13. Examples of a suitable communication medium includecopper wire (such as a coaxial cable), optical fiber, and microwave oroptical link.

The frequency scanner 320 can detect extraneous signals that couldinterfere with the testing process for the uplink integrity detectionsub-system 13. Extraneous signals can include signals from otherwireless devices in the coverage area of the remote antenna unit 120.The frequency scanner 320 can be coupled to antenna 314 via adirectional coupler 322. The frequency scanner 320 can include aspectrum analyzer. The frequency spectrum can be analyzed, for example,by computing a Fast Fourier Transform (“FFT”) of a portion of interestof a digital representation of the frequency spectrum that has beendigitized. A processor, such as a processor of the spectrum analyzer,can compare the power associated with the FFT bins of an appropriatewindow with a power threshold that triggers an identification of anextraneous signal in the uplink path. The processor can provide a windowof the FFT for the portion of the frequency spectrum used by the uplinkintegrity detection sub-system 13. The processor can compare the powerassociated with the FFT bins in the window with a threshold powerassociated with an extraneous signal in the uplink path. The processorcan determine that an FFT bin having a power exceeding the thresholdpower corresponds to an extraneous signal at the frequency correspondingto the FFT bin. The processor can configure the uplink integritydetection sub-system 13 to select a frequency channel for an inputsignal that does not include frequencies corresponding to extraneoussignals detected using the FFT.

In some aspects, the uplink integrity detection sub-system 13 can beimplemented without a frequency scanner. The uplink integrity detectionsub-system 13 can identify extraneous signals by generating test signalsaccording to a pattern. The DAS controller 212 can configure the testsignal generator 302 of a remote antenna unit 120 to generate a testsignal of a given power and/or time interval. The DAS controller 212 cancorrelate the output signal having a certain power and/or at a certaintime with the test signal. The DAS controller 212 can determine that anoutput signal not correlated with the given power and/or time intervalresults from an extraneous signal rather than a test signal.

The frequency scanner 320 can provide information to the processor 304about the frequencies of extraneous signals in the coverage area of theremote antenna unit 120. The processor 304 can provide information aboutthe frequencies of extraneous signals to the DAS controller 212. The DAScontroller 212 can select a test signal frequency such that themeasurement band does not include frequencies of the extraneous signals.The DAS controller 212 can communicate a control signal to the processor304 identifying the test signal frequency. The processor 304 canconfigure the test signal generator 302 to use the test signal frequencywithin the measurement band.

In some aspects, the uplink integrity detection sub-system 13 candetermine the noise figure using, for example, the signal generatortwice power method. The test signal generator 302 can provide a testsignal at a frequency within a measurement band to the receive antennaof the remote antenna unit. The power of the test signal provided by thetest signal generator 302 can be adjusted to produce a three-decibel(dB) increase in the output power measured by the power detector. Theuplink integrity detection sub-system 13 can determine the noise figureusing the measurement bandwidth and the power of the signal provided bythe test signal generator 302. In some aspects, the uplink integritydetection sub-system 13 can iteratively apply this method to determinethe noise figure for each signal path from a remote antenna unit to themaster unit communicating with the remote antenna unit.

FIG. 5 depicts a flow chart illustrating a process 400 for reducing thenoise contribution of a remote antenna unit 120 in a DAS 10 having anexcessive noise figure according to one aspect. The process 400 isdescribed with reference to the DAS 10 depicted in FIG. 2 and the systemimplementation of the uplink integrity detection sub-system 13 depictedin FIGS. 3 and 4. Other implementations and processes, however, arepossible. The DAS controller 212 can apply the process 400 to eachuplink path from a remote antenna unit to the master unit 118 in a DAS.

In block 410, the uplink integrity detection sub-system 13 measures theoutput noise floor of an uplink path selected by the DAS controller 212at a point prior to the combiner module 210. The DAS controller 212 canselect the uplink path via the switches 222 and 208. The switches 222and 208 can be controlled by the DAS controller 212 via the modem 214.The modem 214 can transmit control signals generated by the DAScontroller 212 to the modem 204. The modem 204 can provide the controlsignals from the modem 214 to the processor 202. The control signals canconfigure the processor 202 to configure the switch 208 to select anuplink path from one of the remote antenna units. The power detector 218can measure the output noise floor over a predetermined bandwidth. Thebandwidth over which the power detector 218 accomplishes its task can belimited by the selective filter 219. The power detector 218 can providedata describing the measurement of the noise floor to the DAS controller212.

In block 420, the uplink integrity detection sub-system provides a testsignal to the input of the remote antenna unit communicating through theselected uplink path selected in block 410. The DAS controller 212 cangenerate a control signal to configure the test signal generator 302.The DAS controller 212 can transmit the control signal to the processor304 via the modem 214 and the modem 306. The processor 304 can beconfigured by the control signal to activate the test signal generator302. The processor 304 can configure the test signal generator 302 to beset at a frequency specified by the control signal from the DAScontroller 212. The frequency can be the center frequency of theselective filter 219.

In block 430, the uplink integrity detection sub-system 13 measures anoutput power of the test signal traversing the uplink path selected bythe uplink integrity detection sub-system 13 at a point prior to thecombiner module 210. The output power can be a function of the inputpower as modified by the test signal traversing the uplink path selectedby the uplink integrity detection sub-system 13. The power detector 218can determine the output power of the test signal. The output power ofthe signal provided by the test signal generator 302 can be adjustedsuch that the power level detected by the power detector 218 is doubled.The DAS controller 212 can transmit a feedback signal to the processor304 via the modem 214 and the modem 306. The processor 304 can configurethe test signal generator 302 to modify the output power of the testsignal based on the feedback signal such that the power level detectedby the power detector 218 is doubled.

In block 440, the uplink integrity detection sub-system 13 determines anoise figure of the uplink path from the remote antenna unit 120 to themaster unit 118 at a point prior to the combiner module 210 based on theoutput power of the test signal from the test signal generator 302. Theoutput power of the test can be retrieved by the DAS controller 212 viaa through query transmitted to the processor 304 via the modems 214,306. The processor 304 can generate a response to the query. Theresponse to the query can include the output power of the test signalgenerator 302 and the losses of the coupler 316 to the input of theisolation sub-system 310. The processor 304 can transmit the response tothe DAS controller 212 via the modems 214, 306. The DAS controller 212can compute the equivalent input power at the isolation sub-system 310based on the output power of the test signal generator 302 and thelosses of the coupler 316 to the input of the isolation sub-system 310.

The DAS controller 212 can determine the noise figure using themeasurement bandwidth of the selective filter 219 and the equivalentinput power at the isolation sub-system 310. For example, the noisefigure NF can be calculated as NF=10 log (F), where F represents thenoise factor. F can be calculated as

${F = \frac{P}{{kT}_{o}B}},$where P represents the power of the signal provided by the test signalgenerator 302, kT_(o) represents the thermal noise, and B represent themeasurement bandwidth. The power detector 218 can measure the outputpower resulting from thermal noise of the remote antenna unit 120 (i.e.,the noise level).

The DAS controller 212 can iteratively apply blocks 410-440 to determinethe noise figure for each remote antenna unit. In other aspects, the DAScontroller 212 can use other methods to determine the noise figure ofthe remote antenna unit.

In block 450, the uplink integrity detection sub-system 13 determinesthat the noise figure of the remote antenna unit 120 at a measurementpoint exceeds a threshold noise figure. The measurement point can be,for example, the input to a combiner module 210 of the master unit 118.The DAS controller 212 can determine that the noise figure of the remoteantenna unit 120 exceeds a threshold noise figure by comparing the noisefigure to a threshold noise figure retrieved by the DAS controller 212.The threshold noise figure can be stored in a memory accessible by theDAS controller 212. The threshold noise figure can be a noise figureassociated with an excessive noise contribution from the remote antennaunit 120. The threshold noise figure can be, for example, a maximumnoise figure determined for a remote antenna unit by a manufacturer in atesting environment or other production environment. An excessive noisecontribution can be a noise contribution having a power exceeding theminimum power of uplink signals from other remote antenna units incommunication with the master unit 118. The excessive noise contributioncan decrease the sensitivity of the base station 12 connected to DAS 10,preventing the base station 12 from distinguishing uplink signals fromother remote antenna units.

In block 460, the uplink integrity detection sub-system 13 can report afault condition identifying one or more operators whose coverage islimited by a remote antenna unit having a noise figure that exceeds thethreshold noise figure. The DAS controller 212 can communicate datadescribing the fault condition to an operator network. An operatornetwork can include any telecommunication network communicating withuser devices via the DAS 10. The DAS controller 212 can communicate thedata describing the fault condition via any suitable communicativeconnection to the operator network. For example, the DAS controller 212can communicate the data describing the fault condition wirelessly orvia a cable connection between the DAS controller 212 and one or moredevices of the operator network, such as a local area networkconnection.

In block 470, the uplink integrity detection sub-system 13 configuresthe DAS 10 to minimize the noise contribution of the faulty remoteantenna unit 120. In some aspects, the DAS controller 212 can reduce thegain of an uplink path from the remote antenna unit 120. Reducing thegain of the uplink path from the remote antenna unit 120 can reduce thesignal coverage of the remote antenna unit 120 in a coverage areaserviced by the remote antenna unit 120. In other aspects, the DAScontroller 212 can increase the gain of the respective uplink paths fromone or more other remote antenna units in communication with the masterunit 118. Increasing the gain of the respective uplink paths from one ormore other remote antenna units can shift the dynamic window of themaster unit 118 having a large number of wireless devices in thecoverage areas serviced by the remote antenna units in communicationwith the master unit 118. In other aspects, the DAS controller 212 canadjust the gain of an uplink path from the remote antenna unit by theratio between the threshold noise floor and the measured noise floor ofthe uplink path amplified by the faulty remote antenna unit and themaster unit 118. The threshold noise floor is the thermal noisemultiplied by the threshold noise factor and by the nominal gain of anuplink path.

In additional or alternative aspects, the noise contribution from eachof the remote antenna units 120 can be equalized. In some aspects, thenoise contributions can be equalized by increasing the gain of uplinkpaths from remote antenna units with lower noise figure or lower noiselevel. In other aspects, the noise contributions can be equalized bydecreasing the gain of one or more uplink paths from remote antennaunits with higher noise figure or higher noise level. In other aspects,a combination of increasing the gain of one or more uplink paths fromremote antenna units with lower noise figures or lower noise levels anddecreasing the gain of one or more uplink paths from remote antennaunits with higher noise figures or higher noise levels can be used.

FIG. 6 depicts a flow chart illustrating a process 500 for reducing thenoise contribution of remote antenna units in a DAS according to oneaspect. The process 500 is described with reference to the DAS 10depicted in FIG. 2 and the system implementation of the uplink integritydetection sub-system 13 depicted in FIGS. 3 and 4. Other implementationsand processes, however, are possible.

In block 510, the uplink integrity detection sub-system 13 determinesthe noise figure and the noise floor for a remote antenna unit 120 atthe input to a combiner module 210 of a master unit 118. In someaspects, DAS controller 212 can use the signal generator twice powermethod to determine the noise figure for the remote antenna unit 120, asdescribed above with respect to blocks 410, 420, 430, 440 of process400. In other aspects, the DAS controller 212 can use other methods todetermine the noise figure of the remote antenna unit.

In some aspects, the noise contribution of a remote antenna unit 120 canbe determined using the noise floor without determining the noisefigure.

In block 520, the uplink integrity detection sub-system 13 compares thenoise figure associated with remote antenna unit 120 to a thresholdnoise figure associated with a nominal gain for the uplink path from theremote antenna unit 120 to the master unit 118. The nominal gain of theuplink path from the remote antenna unit 120 to the master unit 118 canbe a gain for the path determined in a testing environment or otherproduction environment.

If the noise figure is less than the threshold noise figure, the uplinkintegrity detection sub-system 13 terminates at block 540.

If the noise figure exceeds the threshold noise figure, the uplinkintegrity detection sub-system 13 compares the output noise floor withthreshold noise floor in block 530. If the measured noise floor is lessthan the threshold noise floor, the process 500 terminates at block 540.

If the output noise floor exceeds the threshold noise floor, the uplinkintegrity detection sub-system 13 adjusts the gain of an uplink pathfrom the remote antenna unit 120 in block 550. The amount of gainadjustment can be determined based on the ratio of the threshold noisefloor to the measured noise floor. For example, the adjust gain can bethe ratio of the threshold noise floor to the measured noise floor. Thegain can be adjusted by modifying the programmable gain of one of theamplifiers 209 a-d in the uplink path from the faulty remote antennaunit. The DAS controller 212 can transmit a control signal to theprocessor 202 via the modems 204, 214 causing the processor 202 toadjust the gain of the amplifier.

Uplink Interference Signals

In additional or alternative aspects, the uplink integrity detectionsub-system 13 can include one or more devices for minimizing orotherwise controlling an undesirable signal component that is aninterfering signal received by a remote antenna unit.

FIG. 7 depicts an example of a remote antenna unit 120′ includingcomponents of the uplink integrity detection sub-system 13 forminimizing or otherwise controlling interfering signals in the uplinkpath 16 from the remote antenna unit 120′ to a master unit. Componentsof the uplink integrity detection sub-system 13 included in the remoteantenna unit 120′ can include a measurement receiver 702, a controller703, amplifiers 704 a, 704 b, and attenuators 706 a, 706 b. The remoteantenna unit 120′ can also include the modem 306, the power amplifier308, the isolation sub-system 310, the power amplifier 308, and anantenna 314.

The remote antenna unit 120′ can receive downlink signals via thedownlink path 14 and provide uplink signals via the uplink path 16. Theisolation sub-system 310 can isolate downlink signals traversing thedownlink path 14 and transmitted via the antenna 314 from uplink signalstraversing the uplink path 16 and recovered via the antenna 314. Theisolation sub-system 310 can be, for example, a duplexer.

An interfering signal can be any extraneous signal recovered by theantenna 314 having a frequency within an uplink frequency band.Extraneous signals can include signals from other wireless devices inthe coverage area of the remote antenna unit 120′. For example, awireless device within a coverage area serviced by the remote antennaunit 120′ may be configured to communicate via a differenttelecommunication system than the DAS 10. Such a wireless device may beconfigured to transmit signals to a base station located at a greaterdistance from the remote device than the remote antenna unit 120′. Thewireless device may transmit signals to the base station at a higherpower than wireless devices configured to communicate via the DAS 10.Interfering signals transmitted at a frequency within the uplinkfrequency band having a higher signal power than uplink signals intendedto be communicated via the DAS 10 can be transmitted to a master unit bythe remote antenna unit 120′. Combing the interfering signal with uplinksignals from other remote antenna units at a master unit can preventuplink signals from other remote antenna units from being distinguishedfrom the interfering signal transmitted by the remote antenna unit 120′.Another example of interfering signals can include two extraneoussignals that can create intermodulation signal products having afrequency within an uplink frequency band.

The measurement receiver 702 can measure the signal power of aninterfering signal received by the remote antenna unit 120′ via theantenna 314. The measurement receiver 702 can periodically scan theuplink frequency spectrum to detect interfering signals. For example,the measurement receiver 702 can be configured to scan the uplinkfrequency spectrum every 150 milliseconds. The measurement receiver 702can be configured to identify signals having a signal power above athreshold signal power. For example, interfering signals from wirelessdevices not communicating via the DAS 10 may have a signal power abovethe threshold signal power used by wireless devices communicating viathe DAS 10. A non-limiting example of a measurement receiver 702 is achannel power detector.

The measurement receiver 702 can be coupled to the antenna 314 via adirectional coupler 710. The measurement receiver 702 can include aspectrum analyzer. The frequency spectrum can be analyzed, for example,by computing an FFT of a portion of a digital representation of thefrequency spectrum. A processor, such as a processor of the spectrumanalyzer, can provide a window of the FFT for the portion of thefrequency spectrum used by the uplink integrity detection sub-system 13.The processor can compare the power associated with the FFT bins in thewindow with a threshold power associated with an extraneous signal inthe uplink path. The processor can determine that an FFT bin having apower exceeding the threshold power corresponds to an interfering signalat the frequency corresponding to the FFT bin.

The measurement receiver 702 can communicate data to the controller 703identifying the interfering signal. The controller 703 can include anysuitable processing device or group of devices. A non-limiting exampleof a controller 703 is a PIC. In some aspects, the measurement receiver702 can communicate data identifying the interfering signal upondetecting the interfering signal. In other aspects, the controller 703can periodically request that the measurement receiver 702 communicatedata identifying the interfering signal.

The controller 703 can generate a control signal for configuring one ormore of the amplifiers 704 a, 704 b and the attenuators 706 a, 706 b.The controller 703 can communicate with the amplifiers 704 a, 704 b andthe attenuators 706 a, 706 b via any suitable mechanism, such as a bus(not depicted). Configuring one or more of the amplifiers 704 a, 704 band the attenuators 706 a, 706 b can include modifying the gain of theuplink signals transmitted by the remote antenna unit 120′.

For example, the controller 703 can receive data from the measurementreceiver 702 identifying an amplitude and a frequency of an interferingsignal. The controller 703 can access one or more data files from amemory device 705, such as a firmware module. The one or more data filescan include specifications for modifying the gain of an uplink signalthat includes the interfering signal. The specifications can identifydifferent gain adjustments for different gain stages. For example, anacceptable signal power for an uplink signal may be −40 dBm. Aninterfering signal may have a signal power of −39 dBm. The controller703 may configure a first gain stage including amplifier 704 a andattenuator 706 a to attenuate all uplink signals by 1 dB. Thespecifications can also identify different gain adjustments specific todifferent interfering signals.

The gain adjusted uplink signal can be converted from an electricalsignal to an optical signal via an electrical-optical (“E/O”) converter708 for transmission to a master unit.

In some aspects, the controller 703 can generate control messages to becommunicated to a DAS controller. A control message can specify anadditional amount of gain adjustment of the uplink signal including theinterfering signal. The control messages can be transmitted to a DAScontroller disposed in a device at another point in the uplink path 16,such as a master unit. In some aspects, modem 306 at the remote antennaunit 120′ can communicate the control message with a modem of anotherdevice in the uplink path 16 via signals transmitted via the uplink path16. In additional or alternative aspects, the modem 306 can communicatewith other devices via a control path. The control path can be anycommunication medium suitable for wired or wireless communicationbetween components of the uplink integrity detection sub-system 13.Examples of a suitable communication medium include copper wire (such asa coaxial cable), optical fiber, and microwave or optical link.

In some aspects, a master unit can include additional components of theuplink integrity detection sub-system 13 for minimizing or otherwisecontrolling an interfering uplink signal received by a remote antennaunit. For example, FIG. 8 depicts an example of a master unit 118′including components of the uplink integrity detection sub-system 13 forminimizing or otherwise controlling interfering signals in the uplinkpath 16 from the remote antenna unit 120′. Components of the uplinkintegrity detection sub-system 13 disposed in the master unit 118′ caninclude a DAS controller 212′, amplifiers 804 a-f, and attenuators 806a-f. The master unit 118′ can also include a splitter module 206 in thedownlink path 14 and a combiner module 210 in the uplink path 16.Examples of the splitter module 206 can include a de-multiplexer,de-serializer, or an optical splitter.

The master unit 118′ can receive optical uplink signals from multipleremote units. The optical uplink signals can be converted to electricaluplink signals by the E/O converters 802 a-c, gain adjusted by one ormore of the amplifiers 804 a-f and attenuators 806 a-f, and combined viathe combiner module 210 for transmission via the uplink path 16.

The DAS controller 212′ can configure one or more of the amplifiers 804a-f and attenuators 806 a-f based on a control message received from aremote antenna unit 120′. An example of a DAS controller 212′ is a PIC.In some aspects, a control message can specify that the gain of theuplink signal including the interfering signal should be increased tooffset an attenuation of the gain at the remote antenna unit 120′. TheDAS controller 212′ can configure one or more of the amplifiers 804 a-fand attenuators 806 a-f in the uplink path from the remote antenna unit120′ to amplify the uplink signal. In other aspects, a control messagecan specify that the gain of the uplink signal including the interferingsignal should be attenuated. The DAS controller 212′ can configure oneor more of the amplifiers 804 a-f and attenuators 806 a-f in the uplinkpath from the remote antenna unit 120′ to attenuate the uplink signal.Configuring the amplifiers 804 a-f and attenuators 806 a-f can include,for example, providing a control signal to the amplifiers 804 a-f andattenuators 806 a-f specifying the gain adjustment.

The master unit 118′ can receive combined downlink signals via thedownlink path 14. The combined downlink signals can be transmitted toindividual remote antenna units via the splitter module 206. Electricaldownlink signals can be converted to optical downlink signals by the E/Oconverters 802 a-c.

The master unit 118′ can communicate periodically with the remoteantenna unit 120′ to determine whether to configure one or more of theamplifiers 804 a-f and attenuators 806 a-f to amplify or attenuate anuplink signal. For example, a master unit 118′ can configure one or moreof the amplifiers 804 a-f and attenuators 806 a-f to amplify orattenuate an uplink signal in response to the remote antenna unit 120′communicating a control message identifying an interfering signal. Themaster unit 118′ can re-configure one or more of the amplifiers 804 a-fand attenuators 806 a-f in response to a second control message from theremote antenna unit 120′ notifying the master unit 118′ that remoteantenna unit 120′ has ceased receiving the interfering signal.

Although FIG. 8 depicts a master unit 118′ in communication with threeremote antenna units, a master unit 118′ can be configured tocommunicate with any number of remote antenna units.

Although an uplink integrity detection sub-system is described withrespect to a DAS, other implementations are possible. For example, theuplink integrity detection sub-system depicted in FIGS. 7 and 8 can beimplemented in a repeater.

The foregoing description of the aspects, including illustrated aspects,of the invention has been presented only for the purpose of illustrationand description and is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Numerous modifications,adaptations, and uses thereof will be apparent to those skilled in theart without departing from the scope of this invention.

What is claimed is:
 1. A distributed antenna system, the systemcomprising: at least one master unit; a plurality of remote antennaunits each in communication with the at least one master unit; and asystem controller configured to: determine a noise figure for an uplinkpath from at least one of the plurality of remote antenna units; andmodify a gain of the uplink path when the noise figure exceeds a desiredthreshold, wherein the noise figure is determined as a function of ameasured signal power of an undesirable signal component in the uplinkpath from the remote antenna unit.
 2. The system of claim 1, wherein thesystem controller determines a respective noise figure and output noisefloor for a respective uplink path from each of the plurality of remoteantenna units.
 3. The system of claim 1, wherein the noise figure isdetermined based on a signal power of the undesirable signal component.4. The system of claim 1, further comprising a test signal generatordisposed in the at least one of the plurality of remote antenna units,wherein the test signal generator is configured to provide a testsignal; wherein the system controller is configured to: determine thenoise figure for the at least one of the plurality of remote antennaunits based on an output power of the test signal; and minimize theundesirable signal component by minimizing a noise contribution of theat least one of the plurality of remote antenna units.
 5. The system ofclaim 4, wherein the system controller is configured to determine thenoise figure based on the output power, a measurement bandwidth, and aninput power of the test signal.
 6. The system of claim 4, wherein thesystem controller is configured to minimize the noise contribution byreducing the gain of the uplink path over which the undesirable signalcomponent is communicated.
 7. The system of claim 4, further comprisinga frequency scanner, wherein the frequency scanner is configured todetermine respective frequencies of one or more extraneous signals in acoverage area of the at least one of the plurality of remote antennaunits; and wherein the test signal generator is configured to providethe test signal at a test frequency such that a measurement bandwidthdoes not include the respective frequencies of the one or moreextraneous signals.
 8. The system of claim 1, wherein the systemcontroller is coupled to a power detector, wherein the power detector isconfigured to measure the output power of an uplink path test signalfrom the at least one of the plurality of remote antenna units at aninput to a combiner module of the at least one master unit.
 9. Thesystem of claim 1, wherein the undesirable signal component comprises awireless interfering signal received by the at least one of theplurality of remote antenna units; wherein the system controllerreceives a control message identifying an amount of gain adjustment ofthe uplink path over which the interfering signal is communicated basedon a signal power of the interfering signal as measured at the at leastone of the plurality of remote antenna units; and wherein the systemcontroller is configured to adjust the gain of the uplink path based onthe amount of gain adjustment.
 10. The system of claim 1, wherein thesystem controller is deposed in one of the at least one master units, azone combiner, or a base station router.
 11. A method for uplink pathintegrity in a distributed antenna system, wherein the distributedantenna system comprises at least one master unit and a plurality ofremote antenna units each in communication with the at least one masterunit, the method comprising: determining with a system controller, anoise figure for an uplink path from a first remote antenna unit of theplurality of remote antenna units; and modifying a gain of the uplinkpath when the noise figure exceeds a desired threshold, wherein thenoise figure is determined as a function of a measured signal power ofan undesirable signal component in the uplink path from the first remoteantenna unit.
 12. The method of claim 11, further comprising:determining with the system controller a respective noise figure andoutput noise floor for a respective uplink path from each of theplurality of remote antenna units.
 13. The method of claim 11, whereinthe noise figure is determined based on a signal power of theundesirable signal component.
 14. The method of claim 11, furthercomprising: generating an upstream test signal from the first remoteantenna unit; determining the noise figure for the first remote antennaunit based on an output power of the test signal; and minimizing theundesirable signal component by minimizing a noise contribution of thefirst remote antenna unit.
 15. The method of claim 14, furthercomprising: determining with the system controller the noise figurebased on the output power, a measurement bandwidth, and an input powerof the test signal.
 16. The method of claim 14, further comprising:minimizing the noise contribution by reducing the gain of the uplinkpath over which the undesirable signal component is communicated. 17.The method of claim 14, further comprising: determining respectivefrequencies of one or more extraneous signals in a coverage area of thefirst remote antenna unit; and providing the test signal at a testfrequency such that a measurement bandwidth does not include therespective frequencies of the one or more extraneous signals.
 18. Themethod of claim 11, further comprising: measuring with a power detectorcoupled to the system controller the output power of an uplink path testsignal from the first remote antenna unit at an input to a combinermodule of the at least one master unit.
 19. The method of claim 11,wherein the undesirable signal component comprises a wirelessinterfering signal received by the first remote antenna unit, the methodfurther comprising: receiving at the system controller a control messageidentifying an amount of gain adjustment of the uplink path over whichthe interfering signal is communicated based on a signal power of theinterfering signal as measured at the first remote antenna unit; andadjusting the gain of the uplink path based on the amount of gainadjustment.
 20. The method of claim 11, wherein the system controller isdeposed in one of the at least one master units, a zone combiner, or abase station router.